FIELD OF INVENTION
This invention relates to foot pedal control mechanisms and apparatus, and more particularly, to a method for engaging and disengaging a power take-off unit associated with the transmission of a heavy duty motor vehicle.
It is well known to those skilled in the art to utilize a so-called power take-off unit in conjunction with a truck or tractor transmission to provide power to a take-off shaft independent of the drive shaft of the vehicle. The power take-off shaft is used to operate an accessory device such as a hydraulic pump or other equipment carried on the vehicle.
In the conventional practice, the power take-off shaft must be engaged and/or disengaged by manual operation of a control lever coupled to a mechanical linkage to actuate the power take-off shaft. An example of such a manually controlled power take-off control mechanism is disclosed by U.S. Pat. No. 2,175,188 to Fuller. This patent discloses a foot pedal operated linkage which directly controls cutting in of a power take-off shaft independently of the propulsion shaft of the vehicle.
A particular problem with such a power take-off control mechanism is that the same must be manually disengaged after operation of the power take-off is complete and normal operation of the vehicle's propulsion shaft is to be resumed.
Since the power take-off shaft is designed to operate at lower revolutions per minute (rpm) than the vehicle's propulsion shaft, the power take-off unit shaft and accessory pump can be severely damaged if the operator fails to disengage the same prior to operating the vehicle at normal driving speed.
Thus, the present invention provides a power take-off release mechanism that is interconnected with the vehicle clutch pedal to automatically disengage the power take-off shaft whenever the vehicle is to be operated at normal driving speeds.